Sfck is a program that locates file changes on your linux system. It keeps a database which you can put on a read-only disk to make sure no changes take place from a hacker/intruder. When a file change is detected it mails root.
You can download it from the following link: https://packetstormsecurity.com/files/download/12831/sfck.tar.gz
Source: https://packetstormsecurity.com/files/12831/sfck.tar.gz.html